Emulsion explosives are well-known in the art; see, for example, U.S. Pat. Nos. 4,356,044; 4,322,258; 4,141,767; and 3,161,551. They generally are formed at elevated temperatures, which are necessary to form the solution of oxidizer salt(s) in water. It has been found, however, that once the emulsion explosive is formed at the elevated temperature, it should be cooled rapidly to ambient temperature in order to preserve its long-term storage stability. Moreover, where such emulsion explosives are chemically gassed for sensitivity purposes, the formulated emulsion should be cooled quickly to minimize shrinkage or potential coalescence of the chemically generated gas bubbles within the emulsion. Accordingly, in forming chemically gassed, packaged emulsion explosives, it is desirable to cool each stick package as quickly as possible.
Packaged explosives have been manufactured for many years. For example, dynamites have been paper-wrapped in conventional machines to form symmetrical cylindrical sticks having crimped or "squared" ends that form planer surfaces perpendicular to the axis of the cylindrical stick. Packages in this form are convenient for handling, and when loaded into boreholes, have good end-to-end contact which facilitates stick-to-stick propagation of a detonation. Aqueous slurry explosives, which comprise a thickened gel of oxidizer salt solution throughout which a fuel is dispersed or dissolved, primarily have been packaged in a sausage-like form in a flexible tubing such as polyethylene having clipped ends. A process and apparatus for packaging slurry explosives in a sausage-like form is described in U.S. Pat. No. 3,783,735. The clipped ends, however, tend to interfere with close end-to-end contact, and thus clipped polyethylene tubes are not as desirable in certain applications as crimped paper tubes in assuring reliable detonation propagation from stick to stick in a loaded borehole. More recently, emulsion explosives have been packaged either in crimped paper tubes, similar to that used for packaging dynamite, or in sausage-like clipped tubes, similar to that used for packaging slurry explosives. Thus for certain applications and for the reasons set forth above, it is desirable to package emulsion explosives in symmetrical paper-wrapped cylinders having squared ends formed by crimping or other means.
Emulsion explosives generally require some form of uniform distribution of gas bubbles for adequate detonation sensitivity. A common method of introducing sensitizing gas bubbles is incorporating a uniform distribution of void containing materials, such as glass or organic microspheres or perlite, throughout the emulsion. These void containing materials will not tend to migrate or coalesce once dispersed throughout the emulsion, and therefore, packaging of emulsions containing these materials is relatively simple.
Another means of sensitizing emulsion explosives is by the introduction of ingredients which react chemically to produce gas bubbles. Chemical gassing is a less expensive means of sensitization than the use of hollow microspheres and is therefore preferred from a cost standpoint. These free, discrete gas bubbles tend to shrink and/or coalesce in the emulsion or escape from the emulsion, however, unless inhibited by the viscosity of the emulsion itself. Because emulsions are relatively fluid at their elevated temperatures, it is important to cool them quickly and render them sufficiently viscous to minimize these problems. Heretofore, gassed emulsion explosives have been manufactured in sausage-like packages that are filled and cooled quickly to prevent gas bubble coalescense. Further, if the emulsion can be cooled prior to packaging, the tacky nature of a hot emulsion can be reduced, thus making the packaging step much easier. Paper wrapping of gassed emulsion in conventional equipment, such as a Rollex machine manufactured by Maschinenfabrik Fr. Neipmann GmbH & Co., has not been possible, since a means for cooling a hot gassed emulsion has not been available. The method of present invention accomplishes, among other things, the critical precooling step.
An additional problem with gassed emulsions is that they tend to shrink in volume as they cool from their elevated formulation temperatures. This is because the volume of an individual gas bubble decreases as the temperature decreases. Thus if gassed emulsions are paper wrapped at their elevated formulation temperatures, undesirable shrinkage within the paper package would occur upon cooling. If the emulsion can be cooled prior to packaging, then this shrinkage problem is eliminated.
Copending and commonly assigned U.S. Ser. No. 128,097 discloses a novel method and apparatus for packaging gassed emulsions. Disclosed herein is another novel method for packaging gassed emulsions, which method can be used with conventional packaging equipment.